DESCRIPTION (Applicant's Abstract): Despite a wealth of information on attention deficit hyperactivity disorder (ADHD) in children, very little exists on its expression in adults. Moreover, current diagnostic criteria, developed on children, do not seem appropriate for adults. Information on the specific forms of impairment associated with ADHD in adulthood and on what methods may be most appropriate for its clinical evaluation is almost nonexistent. Yet, our pilot studies indicate that ADHD in adults significantly predisposes toward specific psychiatric comorbidities and impairments in adaptive functioning, such as social and marital relations, employment difficulties, and child management. A 3 year study is proposed to evaluate the nature of ADHD, the utility of existing and newly proposed sets of symptoms for the development of diagnostic criteria, the value of establishing an age of onset criterion for diagnosis, and the specific psychiatric/psychologic comorbidities associated with ADHD in adults. The manner in which these comorbid disorders affect patterns of impairment will also be studied. A multi-method assessment battery will be utilized and possible effects related to gender will be examined. Specifically, 240 clinic-referred adults with ADHD (120 of each gender) and 160 community control adults (80 of each gender) will be studied. Each will be interviewed concerning psychiatric disorders as well as difficulties in social and psychological functioning, employment, and educational achievement and attainment. Past educational records will also be obtained to evaluate any history of educational impairment since childhood. A battery of neuropsychological tests will be used to assess sustained attention, impulse control, delay of gratification, working memory, sense of time, and planning ability. Results should provide important information about ADHD in adults and potentially useful criteria for its diagnosis.